Re: [PATCH] Makefile: fix parallel build race

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

On Wed, Nov 17 2021, Mike Hommey wrote:

> On Tue, Nov 16, 2021 at 10:18:14PM -0500, Jeff King wrote:
>> On Wed, Nov 17, 2021 at 08:25:55AM +0700, Đoàn Trần Công Danh wrote:
>> 
>> > * builtin/bugreport.c includes hook-list.h, hence generated files from
>> > it must depend on hook-list.h
>> 
>> Good catch. This is trivially reproducible with:
>> 
>>   make clean
>>   make builtin/bugreport.o
>> 
>> The problem comes from cfe853e66b (hook-list.h: add a generated list of
>> hooks, like config-list.h, 2021-09-26), as you might expect.
>> 
>> > diff --git a/Makefile b/Makefile
>> > index 241dc322c0..413503b488 100644
>> > --- a/Makefile
>> > +++ b/Makefile
>> > @@ -2222,6 +2222,7 @@ git$X: git.o GIT-LDFLAGS $(BUILTIN_OBJS) $(GITLIBS)
>> >  
>> >  help.sp help.s help.o: command-list.h
>> >  hook.sp hook.s hook.o: hook-list.h
>> > +builtin/bugreport.sp builtin/bugreport.s builtin/bugreport.o: hook-list.h
>> 
>> This fix looks correct. I grepped for other similar cases, but this is
>> the only file that needs it.
>> 
>> Curiously, the existing hook.c does not seem to include hook-list.h,
>> even though you can see a dependency in the context above. Nor does
>> help.c, which gained a similar dependency in cfe853e66b. Those seem
>> superfluous, but maybe I'm missing something.
>
> Neither does builtin/help.c. This was discussed in the subthread
> starting at https://lore.kernel.org/all/20211115220455.xse7mhbwabrheej4@glandium.org/
> and is covered by https://lore.kernel.org/all/patch-v3-19.23-234b4eb613c-20211116T114334Z-avarab@gmail.com/
> (to which I responded that the line for hook.o can be removed too)

I've got an updated patch in my just-re-rolled Makefile dependency fixes
series for this isuse, which also addresses the needless "hook.{sp,s,o}
-> hook-list.h" dependency issue:
https://lore.kernel.org/git/patch-v4-19.23-2710f8af6cd-20211117T101807Z-avarab@gmail.com/

Thanks again for looking all of this over & helping to make the Makefile
better.